1. Field of the Invention
This invention relates to optical systems, more particularly a method of calibrating such systems.
2. Background of the Invention
Certain optical systems require calibration for optimal performance. For example, systems with sensors, such as Forward-Looking Infrared (FLIR) detection systems, vary in responsivity over time and from pixel to pixel. To overcome this, the operators typically perform some type of calibration. The calibration allows a correction to the sensor reading before the data appears on a display, making the reading more accurate.
This concept applies to other types of systems. Systems that receive scenes in color can use this calibration to adjust for color brightness, balance, and saturation. Similarly, black and white systems could use it to adjust grey-scale readings or outputs.
Problems exist in the current ways calibration occurs. Calibration systems require longer periods of time than desired by the operators. These systems or circuits normally take up quite a bit of space, and use more power than desired. Another significant problem resides in the uniformity of the reference source into the system, and the difficulty of isolating the reference from the sensor during normal operation.
In a FLIR, for example, the calibration occurs using a reference source that has two known temperatures. The temperature mix travels through non-imaging optics to the system sensors. The sensor reads the mix and produces a temperature reading. The difficulty lies in controlling the mix of the two temperatures.